linux-kernel - Re: [mm][PATCH 0/4] Memory cgroup hierarchy introduction

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Date:	Thu, 6 Nov 2008 01:33:06 +0900 (JST)
From:	"KAMEZAWA Hiroyuki" <kamezawa.hiroyu@...fujitsu.com>
To:	balbir@...ux.vnet.ibm.com
Cc:	"KAMEZAWA Hiroyuki" <kamezawa.hiroyu@...fujitsu.com>,
	linux-mm@...ck.org, "YAMAMOTO Takashi" <yamamoto@...inux.co.jp>,
	"Paul Menage" <menage@...gle.com>, lizf@...fujitsu.com,
	linux-kernel@...r.kernel.org,
	"Nick Piggin" <nickpiggin@...oo.com.au>,
	"David Rientjes" <rientjes@...gle.com>,
	"Pavel Emelianov" <xemul@...nvz.org>,
	"Dhaval Giani" <dhaval@...ux.vnet.ibm.com>,
	"Andrew Morton" <akpm@...ux-foundation.org>
Subject: Re: [mm][PATCH 0/4] Memory cgroup hierarchy introduction

Balbir Singh said:
> KAMEZAWA Hiroyuki wrote:
>> On Sun, 02 Nov 2008 00:18:12 +0530
>> Balbir Singh <balbir@...ux.vnet.ibm.com> wrote:
>> As first impression, I think hierarchical LRU management is not
>> good...means
>> not fair from viewpoint of memory management.
>
> Could you elaborate on this further? Is scanning of children during
> reclaim the
> issue? Do you want weighted reclaim for each of the children?
>
No. Consider follwing case
   /root/group_root/group_A
                   /group_B
                   /group_C

  sum of group A, B, C is limited by group_root's limit.

  Now,
        /group_root limit=1G, usage=990M
                    /group_A  usage=600M , no limit, no tasks for a while
                    /group_B  usage=10M  , no limit, no tasks
                    /group_C  usage=380M , no limit, 2 tasks

  A user run a new task in group_B.
  In your algorithm, group_A and B and C's memory are reclaimed
  to the same extent becasue there is no information to show
  "group A's memory are not accessed recently rather than B or C".

  This information is what we want for managing memory.

>> I'd like to show some other possible implementation of
>> try_to_free_mem_cgroup_pages() if I can.
>>
>
> Elaborate please!
>
ok. but, at least, please add
  - per-subtree hierarchy flag.
  - cgroup_lock to walk list of cgroups somewhere.

I already sent my version "shared LRU" just as a hint for you.
It is something extreme but contains something good, I think.

>> Anyway, I have to merge this with mem+swap controller.
>
> Cool! I'll send you an updated version.
>

Synchronized LRU patch may help you.

Thanks,
-Kame


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